Hydroxybenzenes have a wide variety of industrial uses. A number of processes are currently available for the production of hydroxybenzenes. One such process is known as a “cumene process.”
A cumene process begins with the production of cumene from benzene and propylene. The cumene is then oxidized to form cumene hydroperoxide:C6H5C(CH3)2H+O2→C6H5C(CH3)2OOHThe cumene hydroperoxide subsequently is cleaved into phenol and acetone:C6H5C(CH3)2OOH→C6H5OH+(CH3)2CO.The oxidation of other phenylalkyl hydroperoxides generally follows a similar pathway.
The process also generally produces a number of byproducts. In a cumene process, byproducts may include, for example, α-methylstyrene (AMS), acetophenone, dicumylperoxide, and dimethylbenzyl alcohol (DMBA). Less desirable byproducts include, for example, AMS dimer and cumyl phenol (CP).
On an industrial scale, cumene hydroperoxide typically is catalytically cleaved with dilute sulfuric acid at relatively high temperatures. The use of dilute sulfuric acid has a number of disadvantages. One disadvantage is that DMBA tends to dehydrate to AMS. AMS tends to form unwanted byproducts, including but not necessarily limited to AMS dimer and cumyl phenol (CP). Although it is possible to thermally crack AMS dimer and CP to produce AMS and phenol, yields are poor and a substantial amount of labor and equipment are required.
U.S. Pat. No. 6,297,406 describes a process for producing phenol and acetone from cumene hydroperoxide in which the cumene hydroperoxide is contacted with a solid-acid catalyst. The solid-acid catalyst comprises a mixed oxide of cerium and a Group IVB metal. In the examples, the catalyst is used under highly dilute laboratory conditions, including a high initial concentration of acetone and dropwise addition of cumene hydroperoxide.
Dropwise addition of cumene hydroperoxide into a relatively large volume of diluent may produce a number of advantages. For example, the drops of cumene hydroperoxide are expected rapidly to convert to phenol and acetone after addition to the large volume of diluent, and the accumulation of less desirable byproducts (cumyl phenol, dimers of AMS) should be minimized or avoided.
Unfortunately, it is not feasible to produce a large volume of phenol by dropwise addition of cumyl hydroperoxide to a large volume of diluent. The yield of phenol produced by such a process would be too low relative to the labor and equipment that would be required to handle the large volume of diluent.
Catalysts and methods of using catalysts are needed which efficiently cleave phenylalkyl hydroperoxides to produce phenol at high yields relative to the materials being processed.